1. Field of the Invention
The present invention is generally directed to an arrayed optical device and, more specifically, to an arrayed in-line optical device for use in an optical transmission system and/or an optical sensor system.
2. Technical Background
Optical isolators have been utilized in a variety of optical systems to reduce reflections that can have an adverse effect on the operation of the systems, such as disruption of the oscillation of a laser and interference with in-line optical amplifiers. Known optical isolators have implemented a wide variety of components to achieve optical isolation. Normally, in-line optical isolators have polarization independent properties and have utilized birefringent crystal plates (e.g., rutiles), half-wave plates and latching garnets or non-latching garnets with external magnets, for example.
Optical circulators have also been utilized in a variety of optical systems to, for example, couple a bidirectional fiber to both an input fiber and an output fiber. Known optical circulators have also generally exhibited polarization independent properties and have also utilized birefringent crystal plates (e.g., rutiles), half-wave plates and latching garnets or non-latching garnets with external magnets, for example.
A rutile is a birefringent material that typically divides a light ray into at least two orthogonal rays (i.e., an ordinary ray and an extraordinary ray). When implemented in an optical isolator or an optical circulator, at least one rutile normally functions as a walk-off element, with a first rutile typically splitting an incoming optical signal into ordinary and extraordinary component beams and a last (e.g., a second) rutile normally causing the two separate beams to become coincident and reform the original incoming optical signal. When utilized in optical isolators and optical circulators, a latching garnet non-reciprocally rotates the component beams of an input signal, typically, by forty-five degrees and a half-wave plate is generally used to reciprocally rotate the component beams an additional forty-five degrees.
Optical collimators have also been utilized in conjunction with optical isolators and optical circulators. As is well known, a collimator functions to convert divergent beams of radiation or particles (e.g., light rays) into parallel beams. Laser diode (LD) collimating lenses are commonly used in laser beam printers, bar code scanners and sensors. In addition, fiber collimators are widely used in a variety of optical applications (e.g., optical filters). However, commercially available fiber collimator arrays have typically implemented separate lenses, which has increased the cost of the array. For example, one commercially available collimator array has utilized a V-groove array substrate with individually aligned graded-index (GRIN) microlenses and fibers in each V-groove. These GRIN microlenses have generally been produced by an ion-exchange process and normally provide high coupling efficiency and have been utilized as collimators for laser beam printers, bar code scanners, optical isolators, optical circulators and digital versatile disc (DVD) players, as well as miniature objective lenses for medical/industrial endoscopes.
Planar microlens arrays (PMLAs) are one or two dimensional lens arrays formed on a substrate and may include numerous microscopic lenses in various sizes and patterns. Commercially available PMLAs are usually graded-index (GRIN), aspheric or Fresnel lenses. PMLAs have been used in liquid crystal projectors and proposed for use in three dimensional data processing and one or two dimensional laser diode (LD) coupling to fibers.
Due to the recent increase in demand for optical isolators and optical circulators, to be used with dense wavelength division multiplexing (DWDM) systems, reducing the optical isolator and the optical circulator cost has become increasingly important. In general, arrayed configuration is considered as one of the solutions for cost-effective fabrication of optical isolators and optical circulators. However, the effectiveness of optical isolators and optical circulators that use collimating arrays incorporating GRIN, aspheric or Fresnel collimating microlenses, are highly dependent on the configuration of the fiber collimator array and optical isolator or circulator chip. As such, it is important to configure the fiber collimator array and to construct the isolator chip to have superior isolation properties. Further, it is important to configure the fiber collimator array and to construct the circulator chip to have superior properties as a circulator.